Effect of the Amine Hydrochloride Salt on the Antifogging Properties of Amino-Functionalized Polysilsesquioxane

Abstract

A poly[3-(2-aminoethylamino)propyl]silsesquioxane (PAEAPS) film was immersed in 0.5 mol/L hydrogen chloride (HCl) methanolic solution and a poly[3-(2-aminoethylamino)propyl]silsesquioxane hydrochloride (PAEAPS-Cl) film containing the amine hydrochloride salt was prepared for the development of high-performance antifogging materials based on polysilsesquioxane. The PAEAPS-Cl film exhibited a higher water uptake (WU) of 29% and scratch resistance of 4.3 estimated by a nanoindenter than the PAEAPS film (WU = 22% and scratch resistance = 3.2). The introduction of the amine hydrochloride salt structure increased the antifogging properties and surface hardness. 29Si solid-state nuclear magnetic resonance (NMR) spectra indicated that the structure of the siloxane network in the PAEAPS film drastically changed upon hydrolysis by amino groups after exposure to water vapor at 40 °C and 95% relative humidity for 1 h. In the PAEAPS-Cl film, the cleavage of the siloxane network was prevented by the introduction of the amine hydrochloride salt as the neutral group, but the amine hydrochloride salt sometimes induced the morphological change of the PAEAPS-Cl film because of strong hydration and cracks and dimples were observed after exposure to water vapor at 40 °C and 95% relative humidity for 1 h. The poly[3-(2-aminoethylamino)propyl-co-methyl]silsesquioxane hydrochloride (P(AEAP-co-Me)S-Cl) film was prepared by the hydrolysis and polycondensation of 3-(2-aminoethylaminopropyl)triethoxysilane and methyltriethoxysilane, followed by immersion in 0.5 mol/L HCl methanolic solution. The obtained P(AEAP-co-Me)S-Cl film exhibited a WU of 17%, lower than those of the PAEAPS and PAEAPS-Cl films, but cracks and dimples were not observed in the P(AEAP-co-Me)S-Cl film even after exposure to water vapor at 40 °C and 95% relative humidity for 1 h. Furthermore, the introduction of the amine hydrochloride salt structure did not decrease transparency and the PAEAPS-Cl and P(AEAP-co-Me)S-Cl films showed high transparency, similar to the PAEAPS film.